There are a large number of sound sources in an automobile. From the viewpoint of a demand for quietness from noise in inside and outside of a car, various soundproof measures have been taken. In particular, with regard to components (sound sources) that generate loud sounds, such as an engine, a transmission, and a driving system, drastic soundproof measures are required in positions near to the sound sources. Thus, a dedicated soundproof component called a soundproof cover is used. In the case of conventional soundproof covers, highly rigid covers formed by molding a metal, a polyamide, polypropylene, or the like are used as sound-insulating materials and direct noises emitted from the sound sources are insulated by the rigid covers according to the mass law. Moreover, in the case of the rigid covers, since inner reverberating sounds (standing waves) generated by reflection of sounds between the sound sources and the covers increase, as measures thereto, the covers have a structure where a sound-absorbing material is post-attached to the inner surface of the covers or a part thereof facing the sound sources (see, e.g., Patent Documents 1 and 2). However, in these soundproof covers, since the above sound sources frequently possess solid-borne sounds (vibration) in combination, in order to prevent the rigid covers from becoming a new sound source (secondary emission), it is necessary to provide a gap between the covers and the sound sources usually through intervention of a vibration-insulating material such as rubber bush so that the rigid covers may not come into contact with the sound sources. However, there are problems such that the standing waves are leaked from the gap to thereby increase a noise level and thus an expected soundproof effect is not obtained.
In additions since it is difficult to provide a sufficient thickness of a lining sound-absorbing material in a highly concentrated space such as inside of an engine room, the above soundproof cover composed of the rigid cover and the lining sound-absorbing material results in an insufficient effect of reducing sounds. Furthermore, the secondary radiated sounds reflected at the cover inner surfaces repeatedly reflect diffusely between the soundproof cover and the sound source intricately to finally cause a phenomenon of emitting a greater sound that is collected from the narrow gap between the cover edge and the sound source in some cases. Particularly, in the case of the soundproof cover having a large and deep R shape, there arises a case where a reflected sound collected by the principle of parabolic antenna is collected at the cover edge and reflected and thus the mounting of the soundproof cover worsens the noise level. However, since the thickness of the lining sound-absorbing material to be used is limited owing to the clearance between the soundproof cover and the sound source, it is difficult to take measures thereto.    Patent Document 1: JP-A-2003-254081    Patent Document 2: JP-A-2002-347535